On Tue, Oct 23, 2018 at 9:32 AM Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> wrote: > > modify_ldt(2) leaves old LDT mapped after we switch over to the new one. > Memory for the old LDT gets freed and the pages can be re-used. > > Leaving the mapping in place can have security implications. The mapping > is present in userspace copy of page tables and Meltdown-like attack can > read these freed and possibly reused pages. Code looks okay. But: > - /* > - * Did we already have the top level entry allocated? We can't > - * use pgd_none() for this because it doens't do anything on > - * 4-level page table kernels. > - */ > - pgd = pgd_offset(mm, LDT_BASE_ADDR); This looks like an unrelated cleanup. Can it be its own patch?
